Added lookup.c

2 files changed, 105 insertions, 0 deletions

diff --git a/sgsnemu/lookup.c b/sgsnemu/lookup.c
new file mode 100755
index 0000000..02e2491
--- /dev/null
+++ b/sgsnemu/lookup.c
@@ -0,0 +1,80 @@
+/* 
+ * Hash lookup function.
+ * Copyright (C) 2003, 2004 Mondru AB.
+ * 
+ * The contents of this file may be used under the terms of the GNU
+ * General Public License Version 2, provided that the above copyright
+ * notice and this permission notice is included in all copies or
+ * substantial portions of the software.
+ * 
+ */
+
+/**
+ * lookup()
+ * Generates a 32 bit hash.
+ * Based on public domain code by Bob Jenkins
+ * It should be one of the best hash functions around in terms of both
+ * statistical properties and speed. It is NOT recommended for cryptographic
+ * purposes.
+ **/
+unsigned long int lookup( k, length, level)
+register unsigned char *k;         /* the key */
+register unsigned long int length; /* the length of the key */
+register unsigned long int level; /* the previous hash, or an arbitrary value*/
+{
+
+#define mix(a,b,c) \
+{ \
+  a -= b; a -= c; a ^= (c>>13); \
+  b -= c; b -= a; b ^= (a<<8); \
+  c -= a; c -= b; c ^= (b>>13); \
+  a -= b; a -= c; a ^= (c>>12);  \
+  b -= c; b -= a; b ^= (a<<16); \
+  c -= a; c -= b; c ^= (b>>5); \
+  a -= b; a -= c; a ^= (c>>3);  \
+  b -= c; b -= a; b ^= (a<<10); \
+  c -= a; c -= b; c ^= (b>>15); \
+}
+
+  typedef  unsigned long  int  ub4;   /* unsigned 4-byte quantities */
+  typedef  unsigned       char ub1;   /* unsigned 1-byte quantities */
+  register unsigned long int a,b,c,len;
+  
+  /* Set up the internal state */
+  len = length;
+  a = b = 0x9e3779b9;  /* the golden ratio; an arbitrary value */
+  c = level;           /* the previous hash value */
+  
+  /*---------------------------------------- handle most of the key */
+  while (len >= 12)
+    {
+      a += (k[0] +((ub4)k[1]<<8) +((ub4)k[2]<<16) +((ub4)k[3]<<24));
+      b += (k[4] +((ub4)k[5]<<8) +((ub4)k[6]<<16) +((ub4)k[7]<<24));
+      c += (k[8] +((ub4)k[9]<<8) +((ub4)k[10]<<16)+((ub4)k[11]<<24));
+      mix(a,b,c);
+      k += 12; len -= 12;
+    }
+  
+  /*------------------------------------- handle the last 11 bytes */
+  c += length;
+  switch(len)              /* all the case statements fall through */
+    {
+    case 11: c+=((ub4)k[10]<<24);
+    case 10: c+=((ub4)k[9]<<16);
+    case 9 : c+=((ub4)k[8]<<8);
+      /* the first byte of c is reserved for the length */
+    case 8 : b+=((ub4)k[7]<<24);
+    case 7 : b+=((ub4)k[6]<<16);
+    case 6 : b+=((ub4)k[5]<<8);
+    case 5 : b+=k[4];
+    case 4 : a+=((ub4)k[3]<<24);
+    case 3 : a+=((ub4)k[2]<<16);
+    case 2 : a+=((ub4)k[1]<<8);
+    case 1 : a+=k[0];
+      /* case 0: nothing left to add */
+    }
+  mix(a,b,c);
+  /*-------------------------------------------- report the result */
+  return c;
+}
+
diff --git a/sgsnemu/lookup.h b/sgsnemu/lookup.h
new file mode 100755
index 0000000..18b94c1
--- /dev/null
+++ b/sgsnemu/lookup.h
@@ -0,0 +1,25 @@
+/* 
+ * Hash lookup function.
+ * Copyright (C) 2003, 2004 Mondru AB.
+ * 
+ * The contents of this file may be used under the terms of the GNU
+ * General Public License Version 2, provided that the above copyright
+ * notice and this permission notice is included in all copies or
+ * substantial portions of the software.
+ * 
+ */
+
+/**
+ * lookup()
+ * Generates a 32 bit hash.
+ * Based on public domain code by Bob Jenkins
+ * It should be one of the best hash functions around in terms of both
+ * statistical properties and speed. It is NOT recommended for cryptographic
+ * purposes.
+ **/
+
+#ifndef _LOOKUP_H
+#define _LOOKUP_H
+unsigned long int lookup( unsigned char *k, unsigned long int length, unsigned long int level);
+
+#endif	/* !_LOOKUP_H */